1. Field of the Invention
This invention relates to a process for the removal of carbon monoxide from a mixture of organics by its selective oxidation. The process can be used for the oxidation of carbon monoxide from a hydrocarbon and/or a partially oxidized hydrocarbon mixture, such as the mixture resulting from the gas phase catalytic oxidation of n-butane to maleic anhydride with air or oxygen. Significant amounts of carbon monoxide are produced as the by-product of that oxidation (see Triverdi, B. C. and Culbertson, B. M., "Maleic Anhydride", Plenum, N.Y. (1982), Chapter 2).
In commercial processes for the production of maleic anhydride from n-butane, to maximize the overall conversion of n-butane to maleic anhydride, recirculation of the product stream is often necessary. In a typical situation, unreacted n-butane will be separated from the maleic anhydride and is recycled along with other gases to the reactor. Without the separation of carbon monoxide from the product stream, there could be a build up of carbon monoxide in the recirculation process, resulting in a significant explosion hazard. It is useful, therefore, to eliminate the carbon monoxide that occurs in the butane to maleic anhydride reaction, while avoiding butane or maleic anhydride losses to undesirable oxidation products. This can be accomplished, either by eliminating the carbon monoxide at the reactor level by modifying the catalyst or by the elimination of CO in the product stream, by, for example, passing the product stream over an appropriate catalyst bed. The present process selectively removes CO from mixtures containing hydrocarbons and/or partially oxidized hydrocarbons (e.g. maleic anhydride), by passing the mixture over a catalyst composed of Pd or Pt on an inert silica or silica containing vanadium phosphate support at temperatures up to 500.degree. C., in the presence of oxygen.
2. Description of the Prior Art
The prior art discloses numerous processes for the oxidation of carbon monoxide in the presence of hydrogen. However, some of these processes have resulted in concurrent oxidation of the other components of the mixture, causing loss of the desired product and a contaminated product.
U.S. Pat. No. 3,216,783 discloses the preferential, low temperature oxidation of carbon monoxide to carbon dioxide in admixture with a gas stream containing hydrogen, over a supported platinum catalyst. The process results in the preferential oxidation of carbon monoxide and the simultaneous reaction of oxygen with hydrogen to form water.
U.S. Pat. No. 4,400,364 discloses a process for the selective oxidation of carbon monoxide to carbon dioxide in the presence of methacrolein, over a catalyst system comprising specific aluminosilicates having pores no larger than 0.4-0.5 millimicrometers and having within the pores a noble metal or a base metal having the ability to catalyze carbon monoxide oxidation.
N. Y. Chen and P. B. Weisz, "Kinetics and Catalysis", Chemical Engineering Progress Symposium Series, Vol. 63, No. 73, pp. 86 to 89, (1967) disclose the shape-selective oxidation of carbon monoxide and butane, in separate streams over Pt/Na-A zeolite.
U.S. Pat. No. 3,373,110 discloses a process for the preparation of platinum metal containing aluminosilicates whose improved crystallinity are illustrated by catalytic oxidation tests.
Benesi, H. A.; Curtis, R. M.; Struder, H. P., J. Catal. 1968, 10, 328-335 disclose the preparation of supported platinum on silica.